Currently we are converting dir_info to/from lists all the time.
The reason is that dir_info is stored as list of dicts in *.dir files,
but that makes it hard to work with. In addition to that, we will likely
be changing .dir file format in the near future #829, so we need to
abstract away dir_info into something that we won't care how it will be
stored on disk.
Related #3256
Related #4847
* state: add simple reentrance
* state: pass Repo instead of LocalCache
* state: use granularly
Users could still load state preemptively if they want to bulk up
the operations, but other than that tree/cache will just load it
when they need it.
* dvc: use cache state when saving downloaded cache
Related to #4485
* tree: dont compute hash from scratch for output dirs
Fixes#4485
* tree: fix get_hash
Ruslan Kuprieiev
Saugat Pachhai